1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, a printing machine and the like and a process cartridge detachably mounted to the image forming apparatus. More particularly, the present invention relates to an image forming apparatus including a process cartridge having a developing unit and other image forming components, and a reservoir containing toner to be supplied to the developing unit and to the process cartridge itself.
2. Discussion of the Background
A background image forming apparatus includes a detachable process cartridge in which consumable components, such as a developing unit including a developer bearing member and a developer container, an image bearing member, an electric charging unit, a cleaning unit and the like are integrally mounted. When the developer container is empty of toner, the process cartridge is replaced by a new process cartridge, allowing a user to replenish toner and exchange the consumable components at one time. Such a cartridge replacement operation is simpler than others where the replenishment of toner and the exchange of the consumable components are separately performed.
However, when image forming processes repeatedly involve print jobs of images having a large area coverage, a large amount of toner is consumed in a relatively small number of printouts. In these cases, the process cartridge runs out of toner and must be replaced before the other consumable components reach the end of their useful life.
To avoid the above-described waste, a technique has been proposed such that a toner bottle is detachably arranged in the process cartridge to separately replenish the toner from the toner bottle to the developing unit. However, when the toner bottle is replaced, the user firstly needs to remove the process cartridge out of the image forming apparatus before removing the toner bottle from the process cartridge. This makes the toner replenishment process long and complicated.
Another easier technique used in background image forming apparatuses for replacing a toner bottle includes providing the process cartridge and the toner separate from each other and detachably arranged therein. However, since the process cartridge needs to be arranged in the vicinity of the toner bottle, the process cartridge and the toner bottle cannot be flexibly arranged in the image forming apparatus. A flexibility in positioning the process cartridge and the toner bottle is required in order to better utilize space in the image forming apparatus and to allow an overall size reduction, particularly, in full-color image forming apparatuses referring four or more sets of toner bottles and process cartridges. Therefore, the flexibility of positioning toner bottles and process cartridges needs to be increased.
Another technique proposed for improving the background image forming apparatus is to arrange the toner bottle away from the process cartridge and to provide a toner supplying unit for supplying the toner in the toner bottle to a developer container in the process cartridge. This increases the flexibility of positioning the process cartridge and the toner bottle in the background image forming apparatus. However, when the toner bottle is arranged away from the process cartridge, the image forming apparatus is made larger because of additional structure needed to support a toner supplying portion.
Referring to FIG. 1, operations of a background process cartridge 1 are described. This process cartridge 1 is one of a plurality of process cartridges for a background color image forming apparatus (not shown). The plurality of process cartridges have identical structures. Therefore, an explanation will be given focusing on the operations performed by the process cartridge 1.
The process cartridge 1 includes an image bearing member 2 and image forming components, such as a charging unit 3, a developing unit 4 and a drum cleaning unit 5. The developing unit 4 includes a developing sleeve 6 and a developer container 7 having a first developer agitating member 7a and a second developer agitating member 7b. 
The image bearing member 2 is a drum-shaped photoconductive element which forms an electrostatic latent image for a single color toner image on its surface. The image forming components are arranged around the image bearing member 2 and form the single color toner image based on the electrostatic latent image formed on the image bearing member 2. When toner of a predetermined color is supplied to the developer container 7, the first and second developer agitating members 7a and 7b agitate the toner and the first developer agitating member 7a conveys the toner toward a surface of the developing sleeve 6. Concurrently with the operation of transferring the toner to the developing sleeve 6, the image bearing member 2 rotating counterclockwise is charged by the charging unit 3 and irradiated by a laser beam L emitted from an optical writing unit (not shown) so that an electrostatic latent image is formed on a surface of the image bearing member 2. The toner held on the surface of the developing sleeve 6 is transferred to the surface of the image bearing member 2 at a nip portion formed between the developing sleeve 6 and the image bearing member 2, and the single color toner image is formed on the surface of the image bearing member 2. Then, the toner image is transferred onto a transfer medium. Residual toner adhering on the surface of the image bearing member 2 is removed by the drum cleaning unit 5.
As shown in FIG. 1, the laser beam L emitted by the optical writing unit arranged below the process cartridge 1 has to travel over the developer container 7. In a background printer including a process cartridge having such a structure, a toner supplying unit (not shown) has to be provided at a portion where it does not block the laser beam L; therefore, possible locations for the toner supplying unit are limited.
Generally, an open/close mechanism is provided to an engaging portion of the process cartridge 1 and the toner supplying unit and a predetermined space is required to mount members for the engaging portion. Moreover, the toner moves by gravity from the toner supplying unit to the process cartridge 1. However, if the toner supplying unit is arranged to a portion higher than the process cartridge 1, a part of the toner supplying unit occupies a space over the developer container 7, which may result in a blockage of the laser beam L.
In order to avoid the inconvenience of the location of the toner supplying unit, it is proposed that the toner supplying unit be provided next to the developer container 7 of the process cartridge 1.
Referring to FIG. 2, a toner supplying portion 8 provided to the background process cartridge 1 of FIG. 1 is described. The process cartridge 1 further includes the toner supplying portion 8. The toner supplying portion 8 includes a toner conveying shaft 9 having a mylar 9a at an end portion thereof. The toner supplying portion 8 receives the toner supplied from a toner bottle (not shown). The toner conveying shaft 9 is rotated so that the mylar 9a agitates and conveys the toner toward the developer container 7. Namely, the toner in the toner bottle is supplied to the developer container 7 not directly but via the toner supplying portion 8. As shown in FIG. 2, the toner supplying portion 8 needs to be provided in addition to the developer container 7, making the size of the process cartridge 1, and consequently the size of the image forming apparatus also larger.
As described above, in order to increase the flexibility in locating a process cartridge and a toner bottle in an image forming apparatus, it is required to locate the toner bottle at a portion away from the process cartridge, thereby allowing the overall size of the image forming apparatus to be minimized.